Really? I have used similar grinders for the very few knifes I have made but would have thought that getting a hollow grind with something like that would be impossible. Maybe I was using a different belt grinder than you guys. What do you use? How do you get around the heat build up and messing up the temper when working with such thin blades? Trust me I know knives and razors are two different ball games and I just want to learn how to work at that level.

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I fully agree with Charlie! Slow works well, better control, lower heat build up! More is not better in some things and that would be belt speed here. He "Charlie" is the man here. I has done more blades than you can shake a stick at. Trust him. Yes fresh belts do not create the heat that a used belt does. I can vouch for that for sure!!

And lots of dunking in cold water. Grind a couple of seconds, dunk. Grind a couple of seconds, dunk. Etc...
Near the spine or the tang you have a bit more margin, but near the edge you gotta dunk every couple of seconds.
Otherwise you'll see blue flowers blossom on the blade.

Sharp belts, low speed, lots of patience, and lots of dunking.
Especially with high grit belts. They cause more heat buildup than low grit belts.

This is also the main reason why you don't grind an 8" diameter hollow with an 8" diameter wheel. You'll create an enormous surface area that is in touch with the belt, leading to extremely fast heat buildup. Instead, you 'wobble' the blade a bit form edge to spine. That way, there is only a small contact surface. This will reduce the heat buildup because a) the surface is smaller, and b) more material will be removed, meaning the heat gets dissipated partially by shedding the material that had heated up.

Again, near the spine and tang you have some more margin because they act as a heatsink. and even if you overheat locally, it really doesn't matter. But if you grind a surface that fits tightly to the wheel, the edge will flash blue before you know what is happening.